不同预热温度下H13钢表面电弧增材20Cr9Mo3Ni2钢的组织与性能

Microstructure and properties of wire arc additive manufactured 20Cr9Mo3Ni2 steel on H13 steel surface at different preheating temperatures

在H13钢基材上电弧增材制造20Cr9Mo3Ni2钢,研究不同预热温度下制件的宏观形貌、微观组织和力学性能。结果表明,预热温度升高降低制件裂纹形成倾向,预热温度高于300℃时,制件无裂纹出现。预热温度对制件不同部位组织的影响不同,增材区底部和中部组织在无预热和预热温度为150℃时主要为回火马氏体,预热温度为300℃时为回火马氏体和淬火马氏体;预热温度为450℃时,底部为马氏体和少量贝氏体,中部区域主要是马氏体;预热温度对顶部的组织影响较小,顶部组织主要是马氏体和残留奥氏体;不同预热温度和区域的晶间都有少量铁素体存在。H13钢基材热影响区的组织在预热温度低于300℃时为回火马氏体,预热温度为450℃时为粗大的马氏体。随预热温度的升高增材区的抗拉强度升高,伸长率降低,横向抗拉强度略高于纵向抗拉强度,而横向伸长率低于纵向伸长率;结合区的抗拉强度比增材区低,预热温度低于300℃时试样断裂位置位于基材,预热温度为450℃时断裂位置位于基材热影响区。增材区的硬度在无预热和预热温度为150℃时底部和中部低,顶部高;预热温度为450℃时,硬度较高,且从顶部到底部分布比较均匀。可见,预热温度跨越Ms点时组织与性能变化大。

20Cr9Mo3Ni2 steel was deposited on the H13 steel substrate using wire arc additive manufacturing at different preheating temperatures,and the macroscopic morphology,microstructure and mechanical properties of the parts were investigated.The results show that the increase of preheating temperature reduces the tendency of cracking and no crack appears when the preheating temperature is higher than 300℃.The preheating temperature has different effect on the microstructure of different positions in the parts.The microstructure at bottom and middle of the additive zone is mainly tempered martensite when without preheating and preheated at 150 C,and is composed of tempered martensite and quenched martensite when preheated at 300 C.When preheated at 450℃,the microstructure at bottom is composed of martensite and a small amount of bainite,and the middle is mainly martensite.The preheating temperature has a little effect on microstructure of top,and the microstructure is mainly martensite and retained austenite.There is a small amount of ferrite between grains at different preheating temperatures and regions.The microstructure of heat affected zone(HAZ)of the HI3 steel substrate is tempered martensite when preheated below 300℃and coarse martensite when preheated at 450℃.The tensile strength of the additive zone increases with the increase of preheating temperature,while the elongation decreases.The transverse tensile strength is slightly higher than the longitudinal one,while the elongation opposite.The tensile strength of the bonding zone is lower than the additive zone,when the preheating temperature is below 300 C,the fracture position is located in the substrate,and when the preheating temperature is 450℃,the fracture position is located in the heat affected zone of the substrate.The hardness of the additive zone is low at the bottom and middle and high at the top when without preheating and preheated at 150℃,while there is a high and uniform hardness from top to bottom when preheated at 450℃.The results indicate that the microstructure and properties change greatly when the preheating temperature changes across Ms point.